Tetrathiaheterohelicene Phosphanes as Helical-Shaped Chiral Ligands for Catalysis

Monteforte, Marco, Cauteruccio, Silvia, Maiorana, Stefano, Benincori, Tiziana, Forni, Alessandra, Raimondi, Laura, Graiff, Claudia, Tiripicchio, Antonio, Stephenson, G. Richard and Licandro, Emanuela (2011) Tetrathiaheterohelicene Phosphanes as Helical-Shaped Chiral Ligands for Catalysis. European Journal of Organic Chemistry, 2011 (28). pp. 5649-5658. ISSN 1099-0690

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Tetrathia[7]helicene-based phosphanes thiaheliphos (2a), nPr-thiaheliphos (2b) and di-nPr-thiaheliphos (2c) have been prepared from the 2,13-dilithio derivatives of thiahelicenes 1a–c by reaction with an excess of Ph2PCl. Protection of the air-sensitive products as BH3 adducts, from which the phosphanes 2a–c are easily regenerated on heating with ethanol, is described. New rhodium(I) complexes 8 and 9 were obtained by reaction of 2c with [Rh(COD)2]+[BF4]– and [BARF]–, respectively, which were converted by oxidation into the chelating phosphane–phosphane oxide RhI complexes 10 and 11. The monophosphane 5 was similarly prepared, andreaction of the dilithio species with ClP(O)(OEt)2 gave the diphosphonate 17, which was characterized by X-ray crystallography. Comparison of data from DFT calculations (B3LYP/SVP) on 2c, 8 and 10 and X-ray data for 17 reveals a strong tension within the thiaheliphos ligands that is partially relaxed by increasing the Rh–P distances and the bite angle of the chelating ligand. Compound (P)-(+)-1c, obtained by chromatographic resolution, was transformed into optically pure (P)-(+)-2c, which was used in the asymmetric hydrogenation of itaconic acid ester and methyl 2-acetamidoacrylate (product ees up to 40%).

Item Type: Article
Faculty \ School: Faculty of Science > School of Chemistry
Depositing User: Users 2731 not found.
Date Deposited: 10 Jan 2012 14:28
Last Modified: 21 Apr 2020 16:50
URI: https://ueaeprints.uea.ac.uk/id/eprint/36049
DOI: 10.1002/ejoc.201100726

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